The present invention relates to a method for producing a preform for light waveguides. More particularly, the present invention relates to a method for producing a preform for light waveguides wherein at least one glass forming layer is precipitated from a glass-forming gas and/or vapor mixture.
The present invention relates in particular to a method wherein a substrate (basic body) is coated on its exterior to initially produce a preform tube which is subsequently collapsed into a glass rod. From this glass rod, the light waveguide is then drawn. The periodical "IEEE of Quantum Electronics", Vol. QE-18 (1982), page 1418, discloses a process for exterior coating (Outside Vapor Deposition, OVD) wherein a burner is moved axially along a rod. Glass-forming gases and/or vapors are fed to this burner so that it becomes possible to externally deposit glass-forming layers. Such a process has the drawback that no high precipitation rates can be realized with just a single burner. To increase the rate of deposition along the outer surface of the rod in such a process, it is necessary to have a burner which emits a linear flame. However, such a flame contains instabilities which lead to annoying irregularities in the coating.